Stacked battery

ABSTRACT

A main object of the present disclosure is to provide a stacked battery in which sneak current caused by an unevenness of a short circuit resistance among a plurality of cells, is suppressed. The present disclosure achieves the object by providing a stacked battery comprising: a plurality of cells in a thickness direction, wherein the plurality of cells are electrically connected in parallel; each of the plurality of cells includes a cathode current collector with a cathode current collecting tab, a cathode active material layer, a solid electrolyte layer, an anode active material layer, and an anode current collector with an anode current collecting tab, in this order; the stacked battery includes a surface-side cell that is located on a surface side of the stacked battery, and a center-side cell that is located on a center side rather than the surface-side cell; and the surface-side cell and the center-side cell satisfy at least one of: condition i) a resistance of the cathode current collecting tab in the surface-side cell is more than a resistance of the cathode current collecting tab in the center-side cell; and condition ii) a resistance of the anode current collecting tab in the surface-side cell is more than a resistance of the anode current collecting tab in the center-side cell.

TECHNICAL FIELD

The present disclosure relates to a stacked battery.

BACKGROUND ART

Stacked batteries comprising a plurality of cells in a thickness direction are known; wherein each of the plurality of cells includes a cathode current collector, a cathode active material layer, a solid electrolyte layer, an anode active material layer, and an anode current collector, in this order. For example, Patent Literature 1 discloses a lithium ion secondary battery comprising a plurality of unit cells, wherein each of the plurality of unit cells includes: a cathode layer provided with a cathode current collector and a cathode mixture layer; a solid electrolyte layer; and an anode layer provided with an anode current collector and an anode mixture layer. Further, Patent Literature 1 discloses a nail penetration test as a method for evaluating the safety of all solid batteries.

Also, for example, Patent Literature 2 discloses a method for producing a stacked type all solid battery wherein: the stacked type all solid battery comprises a plurality of all solid battery cells connected in a bipolar form or in a monopolar form; and each of the plurality of all solid battery cells includes a cathode current collector layer, a cathode active material layer, a solid electrolyte layer, an anode active material layer, and an anode current collector layer. Also, for example, Patent Literature 3 discloses a secondary battery wherein at least either widths or thicknesses of the current collector leads are varied according to the length of the current collector lead connected to a stacked body among a plurality of stacked bodies.

CITATION LIST Patent Literatures

Patent Literature 1: Japanese Patent Application Laid-Open (JP-A) No. 2016-207614

Patent Literature 2: JP-A No. 2016-136490

Patent Literature 3: JP-A No. 2012-181941

SUMMARY OF DISCLOSURE Technical Problem

As described above, the nail penetration test is known as a method for evaluating the safety of all solid batteries. The nail penetration test is a test of penetrating a conductive nail through an all solid battery, and observing changes (such as a temperature change) when an internal short circuit within the battery occurs.

From detailed studies of the nail penetration test of stacked batteries comprising a plurality of all solid battery cells electrically connected in parallel, the present inventors have acquired new knowledge that the resistance of a short circuit part (short circuit resistance) in each cell varies greatly with the cell location. When a cell with low short circuit resistance and a cell with high short circuit resistance are mixed, a current flows from the cell with high short circuit resistance into the cell with low short circuit resistance. Hereinafter, this may be referred to as a “sneak current”. When the sneak current occurs, the temperature of the cell with low short circuit resistance (the cell to which the current flowed into) increases, and as the result, the battery materials are easily deteriorated.

The present disclosure has been made in view of the above circumstances, and a main object thereof is to provide a stacked battery in which sneak current caused by an unevenness of a short circuit resistance among a plurality of cells, is suppressed.

Solution to Problem

In order to achieve the object, the present disclosure provides a stacked battery comprising: a plurality of cells in a thickness direction, wherein the plurality of cells are electrically connected in parallel; each of the plurality of cells includes a cathode current collector with a cathode current collecting tab, a cathode active material layer, a solid electrolyte layer, an anode active material layer, and an anode current collector with an anode current collecting tab, in this order; the stacked battery includes a surface-side cell that is located on a surface side of the stacked battery, and a center-side cell that is located on a center side rather than the surface-side cell; and the surface-side cell and the center-side cell satisfy at least one of:

condition i) a resistance of the cathode current collecting tab in the surface-side cell is more than a resistance of the cathode current collecting tab in the center-side cell; and condition ii) a resistance of the anode current collecting tab in the surface-side cell is more than a resistance of the anode current collecting tab in the center-side cell.

According to the present disclosure, since the surface-side cell and the center-side cell satisfy at least one of condition i) and condition ii), sneak current caused by an unevenness of a short circuit resistance among a plurality of cells, may be suppressed in a stacked battery.

In the disclosure, a specific resistance of the cathode current collecting tab in the surface-side cell may be more than a specific resistance of the cathode current collecting tab in the center-side cell.

In the disclosure, a specific resistance of the anode current collecting tab in the surface-side cell may be more than a specific resistance of the anode current collecting tab in the center-side cell.

In the disclosure, a thickness of the cathode current collecting tab in the surface-side cell may be less than a thickness of the cathode current collecting tab in the center-side cell.

In the disclosure, a thickness of the anode current collecting tab in the surface-side cell may be less than a thickness of the anode current collecting tab in the center-side cell.

In the disclosure, an area of the cathode current collecting tab in the surface-side cell may be less than an area of the cathode current collecting tab in the center-side cell.

In the disclosure, an area of the anode current collecting tab in the surface-side cell may be less than an area of the anode current collecting tab in the center-side cell.

In the disclosure, the cathode current collecting tab in the surface-side cell may include a resistor on at least one surface side.

In the disclosure, the anode current collecting tab in the surface-side cell may include a resistor on at least one surface side.

In the disclosure, an area of a welded portion in contact with the cathode current collecting tab in the surface-side cell may be less than an area of a welded portion in contact with the cathode current collecting tab in the center-side cell.

In the disclosure, an area of a welded portion in contact with the anode current collecting tab in the surface-side cell may be less than an area of a welded portion in contact with the anode current collecting tab in the center-side cell.

In the disclosure, when each of the plurality of cells is numbered as 1^(st) cell to N^(th) cell, in which N≥3, in order along the thickness direction of the stacked battery, the surface-side cell may be a cell that belongs to a cell region A including 1^(st) cell to (N/3)^(th) cell.

In the disclosure, the center-side cell may be a cell that belongs to a cell region B including ((N/3)+1)^(th) cell to (2N/3)^(th) cell.

In the disclosure, an average resistance of the cathode current collecting tab in the cell region A may be more than an average resistance of the cathode current collecting tab in the cell region B.

In the disclosure, an average resistance of the anode current collecting tab in the cell region A may be more than an average resistance of the anode current collecting tab in the cell region B.

In the disclosure, when each of the plurality of cells is numbered as 1^(st) cell to N^(th) cell, in which N≥60, in order along the thickness direction of the stacked battery, the surface-side cell may be a cell that belongs to a cell region C including 1^(st) cell to 20^(th) cell.

In the disclosure, the center-side cell may be a cell that belongs to a cell region D including 21^(st) cell to 40^(th) cell.

In the disclosure, an average resistance of the cathode current collecting tab in the cell region C may be more than an average resistance of the cathode current collecting tab in the cell region D.

In the disclosure, an average resistance of the anode current collecting tab in the cell region C may be more than an average resistance of the anode current collecting tab in the cell region D.

In the disclosure, the anode active material layer may include Si or a Si alloy as an anode active material.

Advantageous Effects of Disclosure

The stacked battery in the present disclosure effects that sneak current caused by an unevenness of a short circuit resistance among a plurality of cells, is suppressed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view showing an example of the stacked battery of the present disclosure.

FIG. 2 is a schematic cross-sectional view explaining a nail penetration test.

FIG. 3 is a graph showing the relationship between the cell location and the short circuit resistance.

FIG. 4 is an equivalent circuit explaining a sneak current.

FIG. 5 is a schematic cross-sectional view explaining a nail penetration test.

FIG. 6 is a schematic perspective view exemplifying the current collector in the present disclosure.

FIGS. 7A to 7D are schematic perspective views exemplifying the current collecting tab in the present disclosure.

FIGS. 8A to 8E are schematic cross-sectional views exemplifying a method for producing a two-stacked cell.

FIG. 9 is a graph exemplifying a voltage profile in a nail penetration test.

DESCRIPTION OF EMBODIMENTS

The stacked battery of the present disclosure will be hereinafter described in detail. FIG. 1 is a schematic cross-sectional view showing an example of the stacked battery of the present disclosure. Stacked battery 100 shown in FIG. 1 comprises plurality of cells 10 (10A, 10B to 10H to 10N) in a thickness direction; and each of plurality of cells 10 includes cathode current collector 4 with a cathode current collecting tab, cathode active material layer 1, solid electrolyte layer 3, anode active material layer 2, and anode current collector 5 with an anode current collecting tab, in this order. Further, plurality of cells 10 are electrically connected in parallel. A method for connecting the cells in parallel is not particularly limited, and for example, cell 10A and cell 10B shown in FIG. 1 are connected in parallel in a manner that the cells share anode current collector 5. Incidentally, two cells next to each other may or may not share cathode current collector 4 or anode current collector 5. In the latter case, for example, by providing two-layered cathode current collector 4 or two-layered anode current collector 5, the two cells next to each other have cathode current collector 4 or anode current collector 5 individually between the cells.

Also, stacked battery 100 includes surface-side cell 10X that is located on a surface side of stacked battery 100, and center-side cell 10Y that is located on a center side rather than surface-side cell 10X. Further, surface-side cell 10X and center-side cell 10Y feature a configuration they satisfy at least one of:

condition i) a resistance of the tab of cathode current collector 4 (cathode current collecting tab) in surface-side cell 10X is more than a resistance of the tab of cathode current collector 4 (cathode current collecting tab) in center-side cell 10Y; and condition ii) a resistance of the tab of anode current collector 5 (anode current collecting tab) in surface-side cell 10X is more than a resistance of the tab of anode current collector 5 (anode current collecting tab) in center-side cell 10Y.

According to the present disclosure, since the surface-side cell and the center-side cell satisfy at least one of condition i) and condition ii), sneak current caused by an unevenness of a short circuit resistance among a plurality of cells, may be suppressed in the stacked battery. As described above, from detailed studies of the nail penetration test of stacked batteries comprising a plurality of cells electrically connected in parallel, the present inventors have acquired new knowledge that the resistance of a short circuit part (short circuit resistance) in each cell varies greatly with the cell location.

This new knowledge will be explained referring to FIG. 2. As shown in FIG. 2, nail 110 is penetrated into stacked battery 100 comprising plurality of cells 10 (10A, 10B to 10H to 10N) electrically connected in parallel. On this occasion, short circuit resistance R (R_(A), R_(B) to R_(H) to R_(N)) is determined with respect to each cell 10. As the result of such detailed studies, as shown in FIG. 3 for example, it was found out that cell 10A located on the surface side has lower short circuit resistance compared to cell 10H located on the center side. In other words, it was found out that there was the unevenness of short circuit resistance among the plurality of cells.

When a cell with low short circuit resistance and a cell with high short circuit resistance are mixed, a current flows from the cell with high short circuit resistance into the cell with low short circuit resistance. As shown in FIG. 4 for example, when a short circuit occurs within a stacked battery comprising cell 10A and cell 10H electrically connected in parallel in which short circuit resistance R_(A) of cell 10A is lower than short circuit resistance R_(H) of cell 10H, sneak current I flowing from cell 10H into cell 10A occurs in accordance with Ohm's law. When sneak current I occurs, the temperature of cell 10A rises due to Joule heating; as the result, the deterioration of the battery material easily occurs.

Although the reason why the unevenness of short circuit resistance exists among the plurality of cells is not completely clear, it is presumed as follows. As shown in FIG. 5 for example, on the surface side (such as location P₁ in FIG. 3) of the stacked battery, by penetrating nail 110 into cell 10, a state in which cathode current collector 4 and anode current collector 5 are in contact, and a state in which cathode active material layer 1 and anode current collector 5 are in contact, are presumed to occur.

Meanwhile, on the center side (such as location P₂ in FIG. 3) of the stacked battery, since the nail proceeds while dragging the fragment of each member, a state in which the cathode current collector and the anode current collector are not in contact, and a state in which the cathode active material layer and the anode current collector are not in contact, are presumed to occur. For the “state not in contact”, for example, the following states may be supposed: a state in which the fragment of the solid electrolyte layer exists between the two, and a state in which a void exists between the two. As the result, the short circuit resistance will be higher on the center side of the stacked battery.

Incidentally, the behavior of the short circuit resistance on the surface side that is opposite to the nail penetrating surface (such as location P₃ in FIG. 3) of the stacked battery may possibly vary with the constitution of the stacked battery; however, in both of the later described Reference Examples 1 and 2, the short circuit resistance was lowered. The reason therefor is presumed that, since the nail proceeds while dragging the larger amount of the fragment of each member, the cathode current collector and the anode current collector will be in a state electrically connected by the fragment with high electron conductivity.

In contrast, in the present disclosure, since the surface-side cell and the center-side cell satisfy at least one of condition i) and condition ii), sneak current caused by an unevenness of a short circuit resistance among a plurality of cells, may be suppressed in the stacked battery. Specifically, by using a current collecting tab with relatively high resistance for the surface-side cell with low short circuit resistance, and using a current collecting tab with relatively low resistance for the center-side cell with high short circuit resistance, sneak current may be suppressed by the difference of the resistance of the current collecting tabs even when the sneak current caused by an unevenness of a short circuit resistance among a plurality of cells occurs. Incidentally, in the present disclosure, an inclusive term of merely “current collecting tab” may be used for a cathode current collecting tab and an anode current collecting tab.

Also, the problem of suppressing the sneak current caused by an unevenness of a short circuit resistance among a plurality of cells is a problem never occurs in a single cell, that is, a problem peculiar to a stacked battery. Further, in a typical all-solid-type stack battery, since all of the constituting members are solids, a pressure applied to the stacked battery during a nail penetration test will be extremely high. Since a high pressure such as 100 MPa or more at the part where the nail penetrates, and particularly, 400 MPa or more at the tip part of the nail, is applied, the management of the short circuit resistance in a high pressure condition is important. In contrast, in a liquid-based battery, since a void into where the liquid electrolyte penetrates exists in the electrode, a pressure applied to the battery during a nail penetration test will be greatly lower. That is, it is difficult to conceive of managing the short circuit resistance in a high pressure condition, based on the technique of the liquid-based battery.

1. Resistance of Current Collecting Tab

The stacked battery of the present disclosure includes a surface-side cell that is located on a surface side of the stacked battery, and a center-side cell that is located on a center side rather than the surface-side cell. Further, the surface-side cell and the center-side cell satisfy at least one of: condition i) a resistance of the cathode current collecting tab in the surface-side cell is more than a resistance of the cathode current collecting tab in the center-side cell; and condition ii) a resistance of the anode current collecting tab in the surface-side cell is more than a resistance of the anode current collecting tab in the center-side cell.

The stacked battery of the present disclosure usually satisfies at least one condition of: including two kinds or more of the cathode current collecting tabs with a different resistance, and including two kinds or more of the anode current collecting tabs with a different resistance. Here, “surface-side cell” and “center-side cell” in the present disclosure are stipulations for specifying the current collecting tabs with a different resistance. For example, an assumed case is a stacked battery including two kinds of the cathode current collecting tabs (cathode current collecting tab α and cathode current collecting tab β) with a different resistance. Incidentally, the resistances are cathode current collecting tab α>cathode current collecting tab β. When a plurality of cells including the cathode current collecting tab α exist on the surface side of the stacked battery, any one of the plurality of cells may be specified as the surface-side cell. Meanwhile, when a plurality of cells including the cathode current collecting tab β exist on the center side of the stacked battery, any one of the plurality of cells may be specified as the center-side cell. Also, for example, when the stacked battery includes three kinds or more of the cathode current collecting tabs with a different resistance, comparing two cathode current collecting tabs with a different resistance among them, when the magnitude relation of the resistances and the locational relation of the two cathode current collecting tabs (cells) satisfy the specific conditions, the cell including one cathode current collecting tab is specified as the surface-side cell, and the cell including the other cathode current collecting tab is specified as the center-side cell. Incidentally, although the explanation was made exemplifying the cathode current collecting tab, it is much the same for the anode current collecting tab.

When the resistance of the cathode current collecting tab in the surface-side cell is regarded as R₁ and the resistance of the cathode current collecting tab in the center-side cell is regarded as R₂, the value of R₁/R₂ is, for example, 1.1 or more, and may be 10 or more. Meanwhile, the value of R₁/R₂ is, for example, 200 or less. Similarly, when the resistance of the anode current collecting tab in the surface-side cell is regarded as R₃ and the resistance of the anode current collecting tab in the center-side cell is regarded as R₄, a preferable range of R₃/R₄ is similar to that of R₁/R₂. The resistance of the cathode current collecting tab and the anode current collecting tab may be obtained from, for example, the specific resistance and the shape thereof.

In the present disclosure, the resistance of the cathode current collecting tab in the surface-side cell is preferably more than the resistance of the cathode current collecting tab in the center-side cell. Similarly, in the present disclosure, the resistance of the anode current collecting tab in the surface-side cell is preferably more than the resistance of the anode current collecting tab in the center-side cell. Also, examples of a current collector with a current collecting tab may include, as shown in FIG. 6, current collector 50 including electrode contacting part S that comes into contact with an electrode and current collecting tab T in the form of a projection that projects from a side of electrode contacting part S. The resistance of the current collecting tab may be adjusted, for example, by the properties of the current collecting tab, a shape of the current collecting tab, a placement of a resistor, and a welding condition.

(1) Property of Current Collecting Tab

A specific resistance of the cathode current collecting tab in the surface-side cell may be more than a specific resistance of the cathode current collecting tab in the center-side cell. Similarly, a specific resistance of the anode current collecting tab in the surface-side cell may be more than a specific resistance of the anode current collecting tab in the center-side cell. When the material of the current collecting tab differs, the specific resistance also differs. The specific resistances of the materials used for the current collecting tab are exemplified in Table 1.

TABLE 1 Specific Resistance (10⁻⁶Ω · cm) Al 2.65 Cu 1.72 Fe 9.7 SUS 72 Ti 55

In the surface-side cell and the center-side cell, the cathode current collecting tabs may contain the same material whereas the anode current collecting tabs may contain different materials; the cathode current collecting tabs may contain different materials whereas the anode current collecting tabs may contain the same material; and both of the cathode current collecting tabs and the anode current collecting tabs may contain different materials. Incidentally, the current collecting tab is typically formed continuously from the electrode contacting part. That is, the electrode contacting part and the current collecting tab typically include the same material.

(2) Shape of Current Collecting Tab

A thickness of the cathode current collecting tab in the surface-side cell may be less than a thickness of the cathode current collecting tab in the center-side cell. Similarly, a thickness of the anode current collecting tab in the surface-side cell may be less than a thickness of the anode current collecting tab in the center-side cell. For example, as shown in FIG. 7A, the thickness of current collecting tab T_(X) in the surface-side cell may be less than the thickness of current collecting tab T_(Y) in the center-side cell. When the thickness of the current collecting tab is larger, the resistance of the current collecting tab tends to be lower. The difference of the thicknesses is, for example, 30 μm or more, and may be 200 μm or more.

In the surface-side cell and the center-side cell, the cathode current collecting tabs may contain the same material whereas the thickness of the cathode current collecting tabs may be different; and the cathode current collecting tabs may contain different materials as well as the thickness of the cathode current collecting tabs may be different. Similarly, in the surface-side cell and the center-side cell, the anode current collecting tabs may contain the same material whereas the thickness of the anode current collecting tabs may be different; and the anode current collecting tabs may contain different materials as well as the thickness of the anode current collecting tabs may be different.

An area of the cathode current collecting tab in the surface-side cell may be less than an area of the cathode current collecting tab in the center-side cell. Similarly, an area of the anode current collecting tab in the surface-side cell may be less than an area of the anode current collecting tab in the center-side cell. For example, as shown in FIG. 7B, the area (the area in plan view) of current collecting tab T_(X) in the surface-side cell may be less than the area of current collecting tab T_(Y) in the center-side cell. When the area of the current collecting tab is larger, the resistance of the current collecting tab tends to be lower. Incidentally, in FIG. 7B, current collecting tab T_(X) and current collecting tab T_(Y) have the same length in depth direction D; however, have different length in width direction W. The proportion of the area of the current collecting tab T_(Y) in the center-side cell with respect to the area of the current collecting tab T_(X) in the surface-side cell is, for example, 1.2 or more, and may be 2 or more. Meanwhile, the proportion is, for example, 10 or less.

For example, when the material of the current collecting tabs (cathode current collecting tab and anode current collecting tab) in the surface-side cell and the center-side cell are the same, the resistance of the current collecting tabs may be adjusted by the shapes of the current collecting tabs.

(3) Placement of Resistor

The cathode current collecting tab in the surface-side cell may include a resistor on at least one surface side. Similarly, the anode current collecting tab in the surface-side cell may include a resistor on at least one surface side. For example, as shown in FIG. 7C, current collecting tab T_(X) in the surface-side cell may include resistor 20 on at least one surface side. Incidentally, in FIG. 7C, current collecting tab T_(Y) in the center-side cell does not include resistor 20. By providing the resistor, the resistance of the current collecting tab tends to be high. The material of the resistor and the material of the current collecting tab in the surface-side cell may be the same, or may be different. In the latter case, the specific resistance of the resistor is preferably more than the specific resistance of the current collecting tab in the surface-side cell.

For example, when the material and the shape of the current collecting tabs (cathode current collecting tab and anode current collecting tab) in the surface-side cell and the center-side cell are the same, the resistance of the current collecting tabs may be adjusted by placing the resistor.

(4) Welding Condition

An area of a welded portion in contact with the cathode current collecting tab in the surface-side cell may be less than an area of a welded portion in contact with the cathode current collecting tab in the center-side cell. Similarly, an area of a welded portion in contact with the anode current collecting tab in the surface-side cell may be less than an area of a welded portion in contact with the anode current collecting tab in the center-side cell. For example, as shown in FIG. 7D, the area of welded portion 21 in contact with cathode current collecting tab T_(X) in the surface-side cell may be less than the area of welded portion 21 in contact with cathode current collecting tab T_(y) in the center-side cell. Incidentally, in FIG. 7D, a plurality of welded portions 21 are formed on the end face of the current collecting tab. Also, although current collecting tabs T_(X) and T_(Y) have resistors 20 in FIG. 7D, resistors 20 may not be provided.

For example, when the material and the shape of the current collecting tabs (cathode current collecting tab and anode current collecting tab) in the surface-side cell and the center-side cell are the same, the resistance of the current collecting tabs may be adjusted by the area of the welded portion.

2. Constitution of Stacked Battery

Each of the plurality of cells included in the stacked battery is numbered as a 1^(st) cell to a N^(th) cell in order along the thickness direction of the stacked battery. N refers to the total cell number included in the stacked battery; for example, N is 3 or more, may be 10 or more, may be 20 or more, and may be 40 or more. Meanwhile, N is, for example, 200 or less, may be 150 or less, and may be 100 or less.

The surface-side cell is preferably a cell that belongs to a cell region including the 1^(st) cell to a (N/3)^(th) cell. Here, the (N/3)^(th) cell is a cell whose order corresponds to a value obtained by dividing the total cell number N by three. For example, when the total cell number is 60, the (N/3)^(th) cell is a 20^(th) cell. Incidentally, when the (N/3) is not an integer, the (N/3)^(th) cell is specified by rounding off to the nearest integer. Also, the surface-side cell may be, for example, a cell that belongs to a cell region including the 1^(st) cell to the 20^(th) cell, and may be a cell that belongs to a cell region including the 1^(st) cell to a 10^(th) cell.

Also, the surface-side cell may be, for example, a cell that belongs to a cell region including a 5^(th) cell to the (N/3)^(th) cell, and may be a cell that belongs to a cell region including the 10^(th) cell to the (N/3)^(th) cell. As mentioned in the later described Reference Examples 1 and 2, due to the influence of an exterior package such as a laminate film, the short circuit resistance of the 1^(st) cell during a nail penetration may be high in some cases. Therefore, the surface-side cell may be specified, excluding the 1^(st) cell and the neighborhood cells.

Meanwhile, the center-side cell is a cell that is located on the center side rather than the surface-side cell. “Center side” refers to the central side in the thickness direction of the stacked cells. The center-side cell is preferably a cell that belongs to a cell region including a ((N/3)+1)^(th) cell to a (2N/3)^(th) cell. Here, the ((N/3)+1)^(th) cell refers to a cell next to the (N/3)^(th) cell when numbered from the 1^(st) cell. Meanwhile, the (2N/3)^(th) cell is a cell whose order corresponds to a value obtained by dividing the doubled value of the total cell number N by three. For example, when the total cell number is 60, the (2N/3)^(th) cell is a 40^(th) cell. Incidentally, when the (2N/3) is not an integer, the (2N/3)^(th) cell is specified by rounding off to the nearest integer. Also, the center-side cell may be, for example, a cell that belongs to a cell region including the 21^(st) cell to the 40^(th) cell.

Also, a cell region including the 1^(st) cell to the (N/3)^(th) cell is regarded as a cell region A, and a cell region including the ((N/3)+1)^(th) cell to the (2N/3)^(th) cell is regarded as a cell region B. The average resistance R_(AC) of the cathode current collecting tab in the cell region A is preferably more than the average resistance R_(BC) of the cathode current collecting tab in the cell region B. The value of R_(AC)/R_(BC) is, for example, 1.1 or more, and may be 10 or more. Meanwhile, the value of R_(AC)/R_(BC) is, for example, 200 or less. Similarly, the average resistance R_(AA) of the anode current collecting tab in the cell region A is preferably more than the average resistance R_(BA) of the anode current collecting tab in the cell region B. The preferable range of R_(AA)/R_(BA) is similar to that of R_(AC)/R_(BC)

Also, a cell region including the 1^(st) cell to the 20^(th) cell is regarded as a cell region C, and a cell region including the 21^(st) cell to the 40^(th) cell is regarded as a cell region D. The average resistance R_(CC) of the cathode current collecting tab in the cell region C is preferably more than the average resistance R_(DC) of the cathode current collecting tab in the cell region D. The value of R_(CC)/R_(DC) is, for example, 1.1 or more, and may be 10 or more. Meanwhile, the value of R_(CC)/R_(DC) is, for example, 200 or less. Similarly, the average resistance R_(CA) of the anode current collecting tab in the cell region C is preferably more than the average resistance R_(DA) of the anode current collecting tab in the cell region D. The preferable range of R_(CA)/R_(DA) is similar to that of R_(CC)/R_(DC).

Also, in the stacked battery after a nail penetration test, the resistance of the cell with the lowest total of the short circuit resistance and the tab resistance is regarded as R_(Min), and the resistance of the cell with the highest total of the short circuit resistance and the tab resistance is regarded as R_(Max). For example, when a metal active material (particularly Si or an Si alloy) is used as the anode active material, the value of R_(Max)/R_(Min) is preferably 100 or less, and more preferably 5.0 or less. Incidentally, the nail penetration test is carried out under conditions mentioned in the later described Reference Examples 1 and 2.

3. Cell

The cell in the present disclosure includes a cathode current collector, a cathode active material layer, a solid electrolyte layer, an anode active material layer, and an anode current collector, in this order. The cell is typically a cell utilizing Li ion conductivity (a Li ion cell). Also, the cell is preferably a cell capable of being charged and discharged (a secondary battery).

(1) Anode Active Material Layer

The anode active material layer includes at least an anode active material, and may include at least one of a solid electrolyte material, a conductive material, and a binder as required.

The anode active material is not particularly limited, and examples thereof may include a metal active material, a carbon active material, and an oxide active material. Examples of the metal active material may include a simple substance of metal and a metal alloy. Examples of the metal element included in the metal active material may include Si, Sn, In, and Al. The metal alloy is preferably an alloy including the above described metal element as the main component. Examples of the Si alloy may include a Si—Al base alloy, a Si—Sn base alloy, a Si—In base alloy, a Si—Ag base alloy, a Si—Pb base alloy, a Si—Sb base alloy, a Si—Bi base alloy, a Si—Mg base alloy, a Si—Ca base alloy, a Si—Ge base alloy, and a Si—Pb base alloy. Incidentally, the Si—Al based alloy, for example, refers to an alloy including at least Si and Al, may be an alloy including only Si and Al, and may be an alloy further including an additional metal element. It is much the same for the alloys other than the Si-Al based alloy. The metal alloy may be a two-component based alloy, and may be a multicomponent based alloy including three or more components.

Meanwhile, examples of the carbon active material may include a mesocarbon microbead (MCMB), a highly oriented pyrolytic graphite (HOPG), a hard carbon, and a soft carbon. Also, examples of the oxide active material may include a lithium titanate such as Li₄Ti₅O₁₂.

Examples of the shape of the anode active material may include a granular shape. The average particle size (D₅₀) of the anode active material is, for example, within a range of 10 nm to 50 μm, and may be within a range of 100 nm to 20 μm. The proportion of the anode active material in the anode active material layer is, for example, 50% by weight or more, and may be within a range of 60% by weight to 99% by weight.

The solid electrolyte material is not particularly limited, and examples thereof may include an inorganic solid electrolyte material such as a sulfide solid electrolyte material, and an oxide solid electrolyte material. Examples of the sulfide solid electrolyte material may include Li₂S—P₂S₅, Li₂S—P₂S₅—LiI, Li₂S—P₂S₅—LiI—LiBr, Li₂S—P₂S₅—Li₂O, Li₂S—P₂S₅—Li₂O—LiI, Li₂S—SiS₂, Li₂S—SiS₂—LiI, Li₂S—SiS₂—LiBr, Li₂S—SiS₂—LiCl, Li₂S—SiS₂—B₂S₃—LiI, Li₂S—SiS₂—P₂S₅—LiI, Li₂S—B₂S₃, Li₂S—P₂S₅—ZmSn (wherein m and n are respectively a positive number; Z is any one of Ge, Zn, and Ga.), Li₂S—GeS₂, Li₂S—SiS₂—Li₃PO₄, Li₂S—SiS₂—Li_(x)MO_(y) (wherein x and y are respectively a positive number; M is any one of P, Si, Ge, B, Al, Ga, and In.) Incidentally, the above described “Li₂S—P₂S₅” refers to a sulfide solid electrolyte material using a raw material composition including Li₂S and P₂S₅, and it is much the same for other descriptions.

In particular, the sulfide solid electrolyte material is preferably provided with an ion conductor including Li, A (A is at least one kind of P, Si, Ge, Al, and B), and S. Further, the ion conductor preferably includes an anion structure (PS₄ ³⁻ structure, SiS₄ ⁴⁻ structure, GeS₄ ⁴⁻ structure, AlS₃ ³⁻ structure, BS₃ ³⁻ structure) of an ortho-composition, as the main component of an anion. The reason therefor is to obtain a sulfide solid electrolyte material with high chemical stability. The proportion of the anion structure of the ortho-composition among the total anion structures in the ion conductor is preferably 70 mol % or more, and more preferably 90 mol % or more. The proportion of the anion structure of the ortho-composition may be determined by, for example, a Raman spectroscopy, a NMR, and an XPS.

In addition to the ion conductor, the sulfide solid electrolyte material may include a lithium halide. Examples of the lithium halide may include LiF, LiCl, LiBr, and LiI, and among them, LiCl, LiBr, and LiI are preferable. The proportion of LiX (X═I, Cl, Br) in the sulfide solid electrolyte material is, for example, within a range of 5 mol % to 30 mol %, and may be within a range of 15 mol % to 25 mol %.

The solid electrolyte material may be a crystalline material, and may be an amorphous material. Also, the solid electrolyte material may be a glass, and may be a crystallized class (a glass ceramic). Examples of the shape of the solid electrolyte material may include a granular shape.

Examples of the conductive material may include carbon materials such as acetylene black (AB), Ketjen black (KB), carbon fiber, carbon nanotube (CNT), and carbon nanofiber (CNF). Also, examples of the binder may include rubber based binders such as butylene rubber (BR), styrene-butadiene rubber (SBR); and fluoride based binders such as polyvinylidene fluoride (PVDF).

The thickness of the anode active material layer is, for example, within a range of 0.1 μm to 300 μm, and may be within a range of 0.1 μm to 100 μm.

(2) Cathode Active Material Layer

The cathode active material layer includes at least a cathode active material, and may include at least one of a solid electrolyte material, a conductive material, and a binder as required.

The cathode active material is not particularly limited, and examples thereof may include an oxide active material. Examples of the oxide active material may include a rock salt bed type active material such as LiCoO₂, LiMnO₂, LiNiO₂, LiVO₂, and LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂; a spinel type active material such as LiMn₂O₄, Li₄Ti₅O₁₂, and Li(Ni_(0.5)Mn_(1.5))O₄; and an olivine type active material such as LiFePO₄, LiMnPO₄, LiNiPO₄, and LiCoPO₄. Also, as the oxide active material, for example, a LiMn spinel active material represented by Li_(1+x)Mn_(2−x−y)M_(y)O₄ (M is at least one kind of Al, Mg, Co, Fe, Ni, and Zn, and 0<x+y<2), and a lithium titanate may be used.

Also, on a surface of the cathode active material, a coating layer including a Li ion conductive oxide may be formed. The reason therefore is to suppress the reaction between the cathode active material and the solid electrolyte material. Examples of the Li ion conductive oxide may include LiNbO₃, Li₄Ti₅O₁₂, and Li₃PO₄. The thickness of the coating layer is, for example, within a range of 0.1 nm to 100 nm, and may be within a range of 1 nm to 20 nm. The coverage of the coating layer on the cathode active material surface is, for example, 50% or more, and may be 80% or more.

The solid electrolyte material, the conductive material, and the binder used for the cathode active material layer are respectively in the same contents as those described in “(1) Anode active material layer” above; thus, the descriptions herein are omitted. Also, the thickness of the cathode active material layer is, for example, within a range of 0.1 μm to 300 μm, and may be within a range of 0.1 μm to 100 μm.

(3) Solid Electrolyte Layer

The solid electrolyte layer is a layer formed between the cathode active material layer and the anode current collector. Also, the solid electrolyte layer includes at least a solid electrolyte material, and may further include a binder as required. The solid electrolyte material and the binder used for the solid electrolyte layer are respectively in the same contents as those described in “(1) Anode active material layer” above; thus, the descriptions herein are omitted.

The content of the solid electrolyte material in the solid electrolyte layer is, for example, within a range of 10% by weight to 100% by weight, and may be within a range of 50% by weight to 100% by weight. Also, the thickness of the solid electrolyte layer is, for example, within a range of 0.1 μm to 300 μm, and may be within a range of 0.1 μm to 100 μm.

(4) Cathode Current Collector and Anode Current Collector

The cathode current collector collects currents of the above described cathode active material layer, and the anode current collector collects currents of the above described anode active material layer. The metal element included in the cathode current collector is not particularly limited, and examples thereof may include Al, Fe, Ti, Ni, Zn, Cr, Au, and Pt. The cathode current collector may be a simple substance of the metal element, and may be an alloy including the metal element as the main component. Stainless steel (SUS) is an example of the Fe alloy, and SUS304 is preferable.

Examples of the shape of the cathode current collector may include a foil shape and a mesh shape. The thickness of the cathode current collector is, for example, 0.1 μm or more, and may be 1 μm or more. When the cathode current collector is too thin, the current collecting function may be degraded. Meanwhile, the thickness of the cathode current collector is, for example, 1 mm or less, and may be 100 μm or less. When the cathode current collector is too thick, the energy density of a battery may be degraded.

The metal element included in the anode current collector is not particularly limited, and examples thereof may include Cu, Fe, Ti, Ni, Zn, and Co. The anode current collector may be a simple substance of the metal element, and may be an alloy including the metal element as the main component. Stainless steel (SUS) is an example of the Fe alloy, and SUS304 is preferable.

Examples of the shape of the anode current collector may include a foil shape and a mesh shape. The thickness of the anode current collector is, for example, 0.1 μm or more, and may be 1 μm or more. When the anode current collector is too thin, the current collecting function may be degraded. Meanwhile, the thickness of the anode current collector is, for example, 1 mm or less, and may be 100 μm or less. When the anode current collector is too thick, the energy density of a battery may be degraded.

Incidentally, the present disclosure is not limited to the embodiments. The embodiments are exemplification, and any other variations are intended to be included in the technical scope of the present disclosure if they have substantially the same constitution as the technical idea described in the claim of the present disclosure and offer similar operation and effect thereto.

EXAMPLES

The present disclosure will be described in more details. First, in each of Reference Examples 1 and 2, it was confirmed that the unevenness of short circuit resistance among a plurality of cells in a conventional stacked battery was large.

Reference Example 1 Production of Cathode

Using a tumbling fluidized bed granulating-coating machine (manufactured by Powrex Corp.), the cathode active material (Li_(1.15)Ni_(1/3)Co_(1/3)Mn_(1/3)W_(0.005)O₂) was coated with LiNbO₃ in the atmospheric environment. After that, by burning thereof in the atmospheric environment, a coating layer including LiNbO₃ was formed on the surface of the cathode active material. Thereby, a cathode active material having the coating layer on the surface thereof was obtained.

Next, butyl butyrate, 5% by weight butyl butyrate solution of a PVDF based binder (manufactured by Kureha Corp.), the obtained cathode active material, a sulfide solid electrolyte material (Li₂S—P₂S₅ based glass ceramic including LiI and LiBr, average particle size D₅₀=0.8 μm), and a conductive material (a vapor-grown carbon fiber, VGCF, manufactured by Showa Denko K. K.) were added into a propylene (PP) container so as to be cathode active material:sulfide solid electrolyte material:conductive material:binder=85:13:1:1 in the weight ratio. Next, the PP container was stirred for 30 seconds by an ultrasonic dispersion apparatus (UH-50, manufactured by SMT Corp.) Next, the PP container was agitated for 3 minutes by an agitation mixer (TTM-1, manufactured by Sibata Scientific Technology LTD.), and further, was stirred for 30 seconds by the ultrasonic dispersion apparatus to obtain a coating solution.

Next, an Al foil (manufactured by Nippon Foil Mfg. Co. Ltd., a cathode current collector) was prepared. The obtained coating solution was pasted on the Al foil by a blade method using an applicator. The coated electrode was dried naturally, and then, was dried at 100° C. for 30 minutes on a hot plate to form a cathode active material layer on one surface of the cathode current collector. Next, the obtained product was cut according to the size of the battery to obtain a cathode.

Production of Anode

Butyl butyrate, 5% by weight butyl butyrate solution of a PVDF based binder (manufactured by Kureha Corp.), an anode active material (silicon, manufactured by Kojundo Chemical Lab. Co., Ltd., average particle size D₅₀=5 μm), a sulfide solid electrolyte material (Li₂S—P₂S₅ based glass ceramic including LiI and LiBr, average particle size D₅₀=0.8 μm), and a conductive material (a vapor-grown carbon fiber, VGCF, manufactured by Showa Denko K. K.) were added into a PP container so as to be anode active material:sulfide solid electrolyte material:conductive material:binder=55:42:2:1 in the weight ratio. Next, the PP container was stirred for 30 seconds by an ultrasonic dispersion apparatus (UH-50, manufactured by SMT Corp.). Next, the PP container was agitated for 30 minutes by an agitation mixer (TTM-1, manufactured by Sibata Scientific Technology LTD.), and further, was stirred for 30 seconds by the ultrasonic dispersion apparatus to obtain a coating solution.

Next, as shown in FIG. 8A, a Cu foil (anode current collector 5) was prepared. The obtained coating solution was pasted on the Cu foil by a blade method using an applicator. The coated electrode was dried naturally, and then, was dried at 100° C. for 30 minutes on a hot plate. Thereby, as shown in FIG. 8B, anode active material layer 2 was formed on one surface of the Cu foil (anode current collector 5). After that, by the similar treatment, anode active material layer 2 was formed on another surface of the Cu foil (anode current collector 5) as shown in FIG. 8C. Next, the obtained product was cut according to the size of the battery to obtain an anode.

Production of Solid Electrolyte Layer

Heptane, 5% by weight heptane solution of a butylene rubber based binder (manufactured by JSR Corp.), and a sulfide solid electrolyte material (Li₂S—P₂S₅ based glass ceramic including LiI and LiBr, average particle size D₅₀=2.5 μm) were added into a PP container. Next, the PP container was stirred for 30 seconds by an ultrasonic dispersion apparatus (UH-50, manufactured by SMT Corp.). Next, the PP container was agitated for 30 minutes by an agitation mixer (TTM-1, manufactured by Sibata Scientific Technology LTD.), and further, was stirred for 30 seconds by the ultrasonic dispersion apparatus to obtain a coating solution.

Next, an Al foil (manufactured by Nippon Foil Mfg. Co. Ltd.) was prepared. The obtained coating solution was pasted on the Al foil by a blade method using an applicator. The coated electrode was dried naturally, and then, was dried at 100° C. for 30 minutes on a hot plate. Next, the obtained product was cut according to the size of the battery to obtain a transfer member including the Al foil and the solid electrolyte layer.

Production of Evaluation Battery

Each of the two obtained transfer members was placed on the anode active material layers formed on the both sides of the anode current collector, and the product was pressed under the pressure of 4 ton/cm² by a cold isostatic pressing method (CIP method). After that, the Al foils of the transfer members were peeled off. Thereby, as shown in FIG. 8D, solid electrolyte layers 3 were formed on anode active material layers 2. Next, each of the two above obtained cathodes was placed on the solid electrolyte layers formed on the both sides of the anode current collectors, and the product was pressed under the pressure of 4 ton/cm² by the cold isostatic pressing method (CIP method). Thereby, as shown in FIG. 8E, cathode active material layers 1 and cathode current collectors 4 were formed on solid electrolyte layers 3. As described above, a two-stacked cell was obtained. Further, 30 of the obtained two-stacked cells were stacked, and the obtained product was sealed with an aluminum laminate film to obtain an evaluation battery.

Reference Example 2 Production of Anode

Butyl butyrate, 5% by weight butyl butyrate solution of a PVDF based binder (manufactured by Kureha Corp.), an anode active material (natural graphite, manufactured by Nippon Carbon Co., Ltd., average particle size D₅₀=10 μm), and a sulfide solid electrolyte material (Li₂S—P₂S₅ based glass ceramic including LiI and LiBr, average particle size D₅₀=0.8 μm) were added into a PP container so as to be anode active material:sulfide solid electrolyte material:binder=59:40:1 in the weight ratio. Next, the PP container was stirred for 30 seconds by an ultrasonic dispersion apparatus (UH-50, manufactured by SMT Corp.) Next, the PP container was agitated for 30 minutes by an agitation mixer (TTM-1, manufactured by Sibata Scientific Technology LTD.), and further, was stirred for 30 seconds by the ultrasonic dispersion apparatus to obtain a coating solution.

Production of Evaluation Battery

A two-stacked cell was obtained in the same manner as in Reference Example 1 except that the obtained coating solution was used. Further, an evaluation battery was obtained in the same manner as in Reference Example 1 except that 40 of the obtained two-stacked cells were stacked.

Evaluation

A nail penetration test was conducted for each evaluation battery obtained in Reference Examples 1 and 2 under the following conditions.

Charging status: uncharged

Resistance meter: RM3542 manufactured by Hioki E. E. Corp.

Nail: SK (carbon tool steel) material (φ: 8 mm, tip angle: 60°)

Speed of the nail: 25 mm/sec

The short circuit resistance of a cell was obtained from a voltage profile upon the nail penetration. An example of the voltage profile is shown in FIG. 9. As shown in FIG. 9, the voltage of the cell decreases by penetrating the nail. Here, the initial voltage is referred to as V₀, and the minimum voltage upon the nail penetration is referred to as V. Also, the internal resistance of the cell was measured in advance, and the internal resistance is referred to as r. Also, the short circuit resistance of the cell is referred to as R. When presuming that all of the current generated due to the voltage drop upon the nail penetration is the short circuit current, a relationship of V/R=(V₀−V)/r is established. The short circuit resistance R of the cell may be calculated from this relationship. By compiling the voltage profile of each cell, a variation of the short circuit resistance in the thickness direction was confirmed. The results thereof are shown in Table 2 and Table 3. Incidentally, the values of the short circuit resistance in Table 2 and Table 3 are relative values when the short circuit resistance of the 1^(st) cell is 1. Also, the cell close to the nail penetration surface was numbered as the 1^(st) cell.

TABLE 2 <Si> Short circuit N^(th) cell resistance 1 1 10 0.005 20 28859 30 38255 40 671141 50 18121 60 0.026

TABLE 3 <C> Nth Short circuit cell resistance 1 1 10 0.159 40 0.968 60 3.683 80 0.698

As shown in Table 2 and Table 3, in both Reference Examples 1 and 2, the short circuit resistance of the 1^(st) cell was more than the short circuit resistance of the 10^(th) cell. The reason therefor is presumed that upon the nail penetration, the insulating part of the laminate film was dragged in. Also, in Reference Example 1, the short circuit resistance of the 40^(th) cell was more compared to the short circuit resistance of the 1^(st) cell or the 10^(th) cell, and in Reference Example 2, the short circuit resistance of the 60^(th) cell was more compared to the short circuit resistance of the 1^(st) cell or the 10^(th) cell. As described above, the short circuit resistance was less in the surface-side cell, and was more in the center-side cell. Particularly, in Reference Example 1 in which Si was used as the anode active material, the unevenness of the short circuit resistance was extremely large compared to Reference Example 2 in which C was used as the anode active material.

REFERENCE SIGNS LIST

-   1 cathode active material layer -   2 anode active material layer -   3 solid electrolyte layer -   4 cathode current collector -   5 anode current collector -   10 cell -   100 stacked battery -   110 nail 

What is claimed is:
 1. A stacked battery comprising: a plurality of cells in a thickness direction, wherein the plurality of cells are electrically connected in parallel; each of the plurality of cells includes a cathode current collector with a cathode current collecting tab, a cathode active material layer, a solid electrolyte layer, an anode active material layer, and an anode current collector with an anode current collecting tab, in this order; the stacked battery includes a surface-side cell that is located on a surface side of the stacked battery, and a center-side cell that is located on a center side rather than the surface-side cell; and the surface-side cell and the center-side cell satisfy at least one of: condition i) a resistance of the cathode current collecting tab in the surface-side cell is more than a resistance of the cathode current collecting tab in the center-side cell; and condition ii) a resistance of the anode current collecting tab in the surface-side cell is more than a resistance of the anode current collecting tab in the center-side cell.
 2. The stacked battery according to claim 1, wherein a specific resistance of the cathode current collecting tab in the surface-side cell is more than a specific resistance of the cathode current collecting tab in the center-side cell.
 3. The stacked battery according to claim 1, wherein a specific resistance of the anode current collecting tab in the surface-side cell is more than a specific resistance of the anode current collecting tab in the center-side cell.
 4. The stacked battery according to claim 1, wherein a thickness of the cathode current collecting tab in the surface-side cell is less than a thickness of the cathode current collecting tab in the center-side cell.
 5. The stacked battery according to claim 1, wherein a thickness of the anode current collecting tab in the surface-side cell is less than a thickness of the anode current collecting tab in the center-side cell.
 6. The stacked battery according to claim 1, wherein an area of the cathode current collecting tab in the surface-side cell is less than an area of the cathode current collecting tab in the center-side cell.
 7. The stacked battery according to claim 1, wherein an area of the anode current collecting tab in the surface-side cell is less than an area of the anode current collecting tab in the center-side cell.
 8. The stacked battery according to claim 1, wherein the cathode current collecting tab in the surface-side cell includes a resistor on at least one surface side.
 9. The stacked battery according to claim 1, wherein the anode current collecting tab in the surface-side cell includes a resistor on at least one surface side.
 10. The stacked battery according to claim 1, wherein an area of a welded portion in contact with the cathode current collecting tab in the surface-side cell is less than an area of a welded portion in contact with the cathode current collecting tab in the center-side cell.
 11. The stacked battery according claim 1, wherein an area of a welded portion in contact with the anode current collecting tab in the surface-side cell is less than an area of a welded portion in contact with the anode current collecting tab in the center-side cell.
 12. The stacked battery according to claim 1, wherein, when each of the plurality of cells is numbered as 1^(st) cell to N^(th) cell, in which N≥3, in order along the thickness direction of the stacked battery, the surface-side cell is a cell that belongs to a cell region A including 1^(st) cell to (N/3) ^(th) cell.
 13. The stacked battery according to claim 12, wherein the center-side cell is a cell that belongs to a cell region B including ((N/3)+1)^(th) cell to (2N/3)^(th) cell.
 14. The stacked battery according to claim 13, wherein an average resistance of the cathode current collecting tab in the cell region A is more than an average resistance of the cathode current collecting tab in the cell region B.
 15. The stacked battery according to claim 13, wherein an average resistance of the anode current collecting tab in the cell region A is more than an average resistance of the anode current collecting tab in the cell region B.
 16. The stacked battery according to claim 1, wherein, when each of the plurality of cells is numbered as 1^(st) cell to N^(th) cell, in which N≥60, in order along the thickness direction of the stacked battery, the surface-side cell is a cell that belongs to a cell region C including 1^(st) cell to 20^(th) cell.
 17. The stacked battery according to claim 16, wherein the center-side cell is a cell that belongs to a cell region D including 21^(st) cell to 40^(th) cell.
 18. The stacked battery according to claim 17, wherein an average resistance of the cathode current collecting tab in the cell region C is more than an average resistance of the cathode current collecting tab in the cell region D.
 19. The stacked battery according to claim 17, wherein an average resistance of the anode current collecting tab in the cell region C is more than an average resistance of the anode current collecting tab in the cell region D.
 20. The stacked battery according to claim 1, wherein the anode active material layer includes Si or a Si alloy as an anode active material. 